Page 467 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 23 Cancer of the Gastrointestinal Tract 445

rate of 86%. 131 However, definitive RT is usually not required, and distant metastasis. 185,186 If disease is localized to the tonsils
as these tumors can be adequately managed with simple surgical and not infiltrative, then surgery should be considered as part of
Local recurrence is common in cats with multiple
a multimodal treatment protocol. Simple tonsillectomy is almost
resection.
127
VetBooks.ir peripheral odontogenic fibromas and is reported in 73% of 11 cats never curative, but probably should be done bilaterally because of
the high percentage of bilateral disease. Cervical lymphadenec-
135
10
3 months to 8 years after surgical resection.

tomy, especially if the regional LNs are large and fixed, is rarely
Acanthomatous Ameloblastoma curative and should be considered diagnostic only. Regional RT
of the pharyngeal region and cervical LNs can achieve locore-
Surgery or RT is also used in the management of dogs with AA. gional control in more than 75% of cases; however, survival still
Mandibulectomy or maxillectomy is required for surgical resec- remains poor with 1-year survival rates of only 10%. 180,181 Local
tion of AAs because of frequent bone invasion by this benign tumor control and STs were significantly improved in one study
tumor. In one study, 91% of AAs recurred at a mean of 32 days of 22 dogs with tonsillar SCC when RT was combined with a
after marginal excision. 127 Local recurrence rates after either man- variety of different chemotherapy drugs. 181 Cause of death is local
dibulectomy or maxillectomy with appropriate margins are less disease early and systemic disease (usually lung metastasis) later.
than 5%. 13–24,125,128,129 In one study of 263 dogs with AA, com- To date, no known effective chemotherapeutic agents exist for
plete histologic excision was reported in 67%, 75%, and 100% of canine or feline SCC, although cisplatin, carboplatin, doxoru-
dogs with 1.0 cm, 1.5 cm, or 2.0 cm surgical margins, respectively. bicin, vinblastine, and bleomycin have been used with limited
Despite incomplete histologic excision, the local recurrence rate success. 85,181 In one study of 44 dogs with tonsillar SCC treated
was 0%, with a mean follow-up of 33 months. 129 with surgery, RT, and/or chemotherapy, the MST was 179 days
Megavoltage RT, consisting of an alternate day protocol of 4 and dogs presenting with either anorexia or lethargy had signifi-
Gy per fraction to a total of 48 Gy, results in a 3-year PFS rate of cantly shorter STs. 187
80% in dogs with AAs. 131 The overall local recurrence rate with
RT varies from 8% to 18% in two studies of 39 dogs and recur- Lingual
rence was eight times more likely with T3 tumors compared with
T1 and T2 tumors. 130,131 The majority of tumors recur within Lingual tumors are uncommon in cats and dogs. In dogs, tongue
the radiation field, which suggests a higher radiation dose may be tumors account for up to 4% of all oropharyngeal neoplasms. 188
required to achieve higher rates of local tumor control, particu- Neoplasia accounts for up to 54% of canine lingual lesions with
larly for tumors greater than 4 cm in diameter. 131 Other complica- 64% of these being malignant tumors. 138,140,188 The majority of
tions associated with RT include malignant transformation in 5% these tumors are located on the dorsal surface of the tongue, and
to 18% of dogs and bone necrosis in 6% of dogs. 130–132 are evenly distributed between the rostral, mid, and caudal por-
Intralesional bleomycin has been reported in two studies of tions of the tongue. 138,141 For unknown reasons, 16% of dogs
dogs with AA. 133,134 In total, 10 dogs were treated with curative- and up to 29% of people with tongue tumors have a second pri-
intent intralesional bleomycin and all had complete responses. In mary tumor. 189 Hence, thorough physical examination and clini-
one study of six dogs, 134 1 to 16 (median, 5) intralesional injec- cal staging are important in animals with tongue tumors. White
tions were administered before a complete response was achieved. dogs appear to be at higher risk for SCC, even though lack of
The median time to complete response was 1.5 months. There pigment would not be intuitive as an etiologic contributor as it
was no evidence of recurrence at 1 year in one study and after a is in other more sunlight-exposed areas of the body (e.g., nose,
median follow-up of 842 days in another study. 134 eyelids, and ears). 139 Other reported breed predilections include
Chow Chow and Chinese Shar-Pei for MM; poodle, Labrador
Selected Sites or Cancer Conditions in the retriever, and Samoyed for SCC; border collie and golden retriever
Oral Cavity for hemangiosarcoma and FSA; and cocker spaniel for plasma
The most common cancer of the canine tongue is
cell tumors.
188
Tonsillar Squamous Cell Carcinoma SCC, accounting for up to 50% of cases, followed by MM, mast
cell tumor, hemangiosarcoma and hemangioma, granular cell
Tonsillar SCC is 10 times more common in animals living in myoblastoma, FSA, adenocarcinoma, neurofibrosarcoma, leio-
urban versus rural areas, implying an etiologic association with myosarcoma, rhabdomyoma and rhabdomyosarcoma, myxoma,
environmental pollutants. 184 The most common tonsillar tumor and lipoma. 139,141,188,190 Feline tongue tumors are usually SCCs,
is SCC. 185,186 Tonsillar SCC has a significantly higher propor- and most are located on the ventral surface near the frenulum.
tion of grade III lesions and metastatic disease at diagnosis com- Presenting signs are similar to those of other oral tumors. Ulcer-
pared with oral SCC at other sites. Lymphoma can affect the ation is common with SCC.
77
tonsils, but bilateral tonsillar involvement is more common An incisional biopsy, such as a punch or wedge biopsy, is rec-
and this is usually accompanied by generalized lymphadenopa- ommended for the diagnosis of tongue lesions in cats and dogs.
thy. 185,186 Other cancers, especially MM, can metastasize to the A biopsy is necessary to differentiate malignant tumors from non-
tonsils. 185,186 Cervical lymphadenopathy is a common present- neoplastic lesions, such as eosinophilic granuloma and calcinosis
ing sign, even with very small primary tonsillar cancers. FNA circumscripta, and because a knowledge of the definitive diagnosis
of the regional LNs or excisional biopsy of the tonsil are required may change treatment options (i.e., surgical dose or multimodality
for definitive diagnosis. Up to 20% of cases have evidence of pul- therapy with either RT and/or chemotherapy) or the willingness
monary metastasis at presentation. In spite of disease apparently of the owner to pursue curative-intent treatment. Ultrasonogra-
confined to the tonsil, this disease is considered systemic at diag- phy can be useful in delineating the margins of tongue masses
nosis in more than 90% of cats and dogs. 185,186 The CT features to determine surgical resectability. 191 Regional LNs should be
of pharyngeal neoplasia have been described, and these are useful aspirated for staging purposes and three-view thoracic radiographs
in determining the extent of local disease and the presence of LN evaluated for lung metastasis.